Filter



Patented Oct. 13, 1925.

UNITED STATES 1,557,234 PATENT OFFICE.

HEINRICH BECHHOLD, OF FRANKFORT-O'N-THE-MAIN, GERMANY.

FILTER.

No Drawing. Continuation of application Serial No. 585,087, filed August 29, 1922. This application filed September 14, 1923. Serial No. 662,755.

To all whom it may concern:

Be it known .that I, HEINRICH BEOHHOLD, a citizen of Germany, residing at Frankforton-the-Main, Germany, have invented certain new and useful Improvements in or Relating to Filters, of which the followlng is a specification.

This invention relates to filters composed of diatomaceous earth, cellulose, clay, carbon and other materials, adapted to filter water, fruit juices, serum, toxin and other liquids.

Although the filters at present in use are well adapted to retain for a certain time micro-organisms, these ver soon grow through the pores of the lter with the result that in a comparatively short time the filtered liquid becomes infected.

For the purpose of destroying microorganisms in liquids, such as water, milk, etc., it has heretofore been suggested to passthe liquid through a bed or layer of grains of sand or other suitable material which has been coated with silver or gold or copper in the form of a colloidal film. Experiments, however, have shown that filter beds treated in this way are ineiiective to retard the growing through of germs except for a relatively short period of time.

Experiments by theapplicant have shown that the growing of bacteria through a porous filter can be prevented if the porous filtermass is uniformly impregnated with insoluble or difiicultly soluble compounds of metals having a lower solution tension than hydrogen and a higher solution tension than platinum. 4

The more important of this group of metals are copper, silver and mercury. However the insoluble compounds of silver and mercury are much more efiective than the insoluble compounds of copper. Of comparatively less importance are bismuth, antimony and arsenic. The followin compounds may be mentioned, by way 0 example, as effective and usable impregnating materials: copper oxide, copper ferrocyanate, copper carbonate, silver chloride, silver oxide, silver sulphocyanate, mercuric oxide and mercurous chloride. The oxides of bismuth and antimony, the sulphides of arsenic and the like can also be used, but

with less effective results.

It is possible to obtain good results with 'nating materials.

a filter impregnated with a single compound of 'a metal having the character specified, for example silver chloride or copper oxide. A filter so impregnated will prevent the growing through of bacteria for a long time.

However, better results are obtained if in addition to a principal impregnating mater1al an activating material is used. As 'acoxide as principal ingredient and silver chloride or silver or' copper or mercurous chloride, as activator. Here all the-components belong to the group of principal ingredients. In another example, silver chloride or copper oxide is the principal ingredient with an addition of gold or platinum as activator.

Generally it proved to be advantageous to use the principal ingredient in predominant quantityvwith a relatively small quantity of activating material. Working with two or more substances from the group of principal ingredients of which one is employed as a principal ingredient and the other as an activator, it proved advanta-, geous to use the substance having the higher solution tension as activator. Excellent results were obtained with filters which had been impregnated with silver chloride as principal ingredient and with platinum as an activator, the silver chloride forming 2% of the weight of the filter and the platinum only a small fraction of the silver chloride.

It is within the scope of the invention to use two or more. activating ingredients instead of one. K could be used as the principal ingredient and relatively small quantities of silver and gold as activator. Instead-of one principal ingredient for impregnation of the filter two For example copper oxide or more could be used. For example, equal parts of copper oxide and silver chloride chloride, with a small quantity of a single activating substance, such as gold or-platinum, gives very satisfactory results.

The following experiment will serve by way of example to illustrate the superiority of a filter treated according to the present invention over a filter which has been impregnated with a single metal, for example, silver Water infected with bacterium coli was passed through three equal kieselguhr filters. The first filter was not impregnated at all. The second filter was impregnated with silver, the quantity of silver incorporated therein amounting approximately to 2% of theweight of the filtering mass. The third filter was impregnated with 2% of silver chloride and with a relatively Small quantity of gold sulphide. Initially all three filtrate infected by bacterium c0l1.- After.

six'days the filter impregnated with silver gave a filtrate infected'with bacteriumcoli, while the filter impregnated with silver chloride and gold sulphide gave a filtrate free of bacteria even after several months. Other bacteria, such as. B. typhoslis, B. paratyphosus, etc, were prevented from passing or growing through the filter. Even sprophyte'water bacteria which as is wellkno-wn grow particularl quickl were prevented or mont s from growing through filters impregnated in accordance with the present invention.

through filters The present application is a continuation of my application, Serial Number 585,087, filed Aug. 29, 1922, Patent Number 1,473,331.

I claim: 1. A filter impregnated with an insoluble or difiicultly soluble compound of a metal of lower solution tension than hydrogen and of ahigher solution tension than copper.

2. A filter impregnated with an insoluble or diflicultly soluble compound of silver.

3. A filter impregnated. with chloride of silver. filters gave a filtrate free of bacteria. After In testimony whereof Ifaflix my signature.

HEINRICH BECHHQLD. he 

